2Full professor of the graduate program in Dermatology at the Catholic University of Rio de Janeiro (Pontificia Universidade Catolica do Rio de Janeiro - PUCRJ). Head of Dermatology at Souza Marques Technical and Educational Foundation (Fundação Tecnico Educacional Souza Marques); Head of the Departament of Dermatology at the Dermatology Institute “Professor Rubem David Azulay”, Charity Hospital of Rio de Janeiro (Instituto de Dermatologia Professor Rubem David Azulay - Santa Casa da Misericordia do Rio de Janeiro - IDPRDA-SCMRJ) – Rio de Janeiro (RJ), Brazil

Shiitake Dermatitis is often presented as papules and erythemato-violaceous linear
streaks. It can be associated with bleomycin treatment, dermatomyositis and shiitake
mushroom (Lentinus edodes). There is not any previous report concerning this rare
etiology in our country. Shiitake is the second most consumed mushroom worldwide and
it can cause flagellate erythema when ingested raw or half cooked. It has a higher
incidence in Oriental countries because of their eating habits, this is the first
case reported in Brazil, in a male patient that presented a cutaneous rash after
consuming this raw mushroom.

Flagellate Erythema is characterized by erythematous violaceous linear grouped papules
and sometimes petechiae resembling whiplash marks.1,2 It was described for the first time by Moulin in 1970, associated with bleomycin
treatment.3 Flagellate erythema has also been associated with the use of other drugs such as
peplomycin (a bleomycin derivate), inflammatory diseases (dermatomyositis and
adult-onset Still's disease) and, most recently, shiitake mushroom
(Lentinus edodes).1Shiitake is the second most consumed mushroom in the world and it can
cause Flagellate Erythema when consumed raw or half cooked.4,5

We report the case for its uncommon etiology and because in a literature review there
were no reported cases of flagellate erythema caused by shiitake in
Brazil, a country with a varied diet that includes ingestion of large amounts of this
mushroom.

CASE REPORT

Male patient, 30 years old, white, born and living in Rio de Janeiro, RJ, Brazil,
complained of intense pruritus followed by disseminated erythematous lesions with onset
less than 24 hours before. He had no history of associated diseases, use of any
medications or any other associated factors. On the first inspection we noted small
erythematous papules and some petechiae that assumed a linear pattern located on the
trunk, lower and upper limbs. There were no mucosal abnormalities, fever or any other
systemic symptoms (Figures 1 and 2). Based on the peculiar rash, the patient was
questioned about the ingestion of shiitake and confirmed he had eaten a
large amount of raw mushrooms five hours before the cutaneous lesions appeared, leading
us to the diagnosis of flagellate erythema due to shiitake
ingestion.

FIGURE 1 Shiitake Dermatitis: clinical features. Small erythematous papules and some
petechiae that assumed a linear pattern located on the trunk and arms

FIGURE 2 Shiitake Dermatitis: clinical features. Small erythematous papules and some
petechiae that assumed a linear pattern located on the left shoulder

DISCUSSION

Flagellate Erythema or Shiitake Dermatitis, also known as toxicoderma
or mushroom workers' disease, occurs after eating raw or half cooked
shiitake or in people who cultivate the mushroom.1,3Shiitake is the second most consumed mushroom worldwide; due to its
polysaccharide properties, lentinan, it is used in Japan for immune system modulation,
lowering of blood pressure and serum cholesterol and also as an antitumor adjuvant drug
in gastric and colorectal cancer.4,5,6,7

Clinical features include very small erythematous papules and eventually petechiae
associated with severe pruritus; the act of scratching and Köebner phenomenon lead to
the linear groups of these papules.1,4,5,7 The skin eruption appears one or two days after eating the mushrooms and usually
involves the trunk, extremities, neck and face. Our patient had similar manifestations a
few hours after consuming the mushroom.4

Unlike the flagellate erythema due to bleomycin, shiitake dermatitis
does not affect mucous membranes nor does it induce pigmentation.1,4 Skin lesions tend to disappear in about two weeks but our patient had a faster
resolution in only three days and mild hyperpigmentation (Figure 3). Differential diagnosis includes other causes of flagellate
erythema such as drug eruptions (bleomycin) and dermatomyositis.

FIGURE 3 Shiitake Dermatitis: clinical evolution. Resolution after three days with mild
hyperpigmentation

It is a self-limited condition, therefore the treatment is basically symptomatic. Since
pruritus is one of the major complains, it can be controlled with sedatives,
antihistamines and topical corticosteroids.3

The diagnosis is made through the characteristic history and typical skin lesions. It is
important to note that there are no specific laboratorial or histopathological
findings.4,6,7 The histological evaluation of a lesion located on our patient's left shoulder
had the following findings: the epidermis was preserved, the dermis showed papillary
edema, erythrocyte overflow, superficial and perivascular infiltrates of mononuclear
cells, without vasculitis or pigmentary incontinence (Figure 4). In the literature, histologic findings are similar, with
nonspecific spongiotic dermatitis.1,4

The underlying pathogenesis is still not well established; some authors consider that
the lentinan could induce a direct toxic skin reaction, other authors submitted their
patients to patch and prick tests that came out positive, and they believe that the
answer is a late onset hypersensitivity.4,5,7 Based on literature data, there are immunologic and non-immunologic factors
involved, the toxic mechanism being the most common.

In Japan and China this dermatitis has a higher prevalence related to the eating habits
of the population, but there are few cases reported in the Occident and this is the
first case reported in Brazil.5,7 Although there is a recent report of a case published in Brazilian literature,
the same happened in Germany.8

In 1992, Nakamura predicted a gradual increase in incidence of shiitake
dermatitis because of the increasing production and ingestion of this mushroom.4 There are new reports from Oriental and Occidental countries. Lentinan is a
thermolabile polysaccharide, therefore it is important to raise awareness that the
ingestion of only well cooked shiitake can prevent this
dermatitis.5,7